week-17

void setup(){

  size(300,300);
}
float x=200,y=150;
void draw(){
  background(#002966);
  stroke(#b7efff);
  line(100,150,x,y);
  fill(#be7fff);
  noStroke();
  ellipse(100,150,13,13);
  ellipse(x,y,13,13);
  if( !mousePressed){                                             不管怎摸拉放掉後都會回到100的位子
  float dx=x-100, dy=y-150;
  float len=sqrt(dx*dx+dy*dy);
  x -=dx*(len-100)/len;
  y -=dy*(len-100)/len;
 
  }
}
void mouseDragged(){
  x=mouseX; y=mouseY;
}